Spring has most definitely sprung, and this is the time when most growth happens on the trees in our bonsai collections. Watering should now be done daily, unless rain occurs. Check afterwards that the soil is moist and the rain has penetrated the soil, as showers combined with wind may mean that you still need to water. As usual, inspect trees which are in full sun more carefully. It’s also important to fertilise your trees regularly, as they should all be in active growth by now. Be sure to follow the directions for the use of whichever product you choose and remember not to feed freshly repotted trees until they return to active growth.
The weather can be changeable at this time of year, with hot days followed by slightly cooler conditions. Trees in full leaf will require more water than those that are still dormant or just coming into bud. Protect trees such as azaleas, camellias, hornbeams and zelkovas from the sun as it becomes hotter, by moving them to semi shade. This will help prevent damage to their foliage.
Continue trimming back new growth to encourage short intermodal spaces, which will mean finer branching on your deciduous bonsai. Maples are notorious for requiring constant attention during spring. The normal practice, at this time, is to allow two or three sets of leaves to open on each branchlet and then prune back to the first new pair of leaves. Then where there were two leaves before, the tree will branch into four leaves, and so on. The exception to this pruning technique on maples is where you want a branch to lengthen or thicken to improve your overall design. In this case, allow the branch to grow unpruned for as long as appropriate. The more diligent you are at this time of year the better your tree will look in the future.
You may have some plants that have flowered earlier in the season, such as wisteria or azaleas, so don’t forget to remove spent flowers. Wisterias will begin to grow quite quickly now and so can be pruned back hard, as needed, until December when you should get another flush of growth. Azaleas can be trimmed and repotted after flowering is finished (even during flowering) before the new growth begins. Be aware that the multiple ‘whorled’ shoots that come behind the spent flowers on azaleas must not all be allowed to grow. Choose one or two that you want to keep at each point for the design of the bonsai and remove the others. Remember that spent flowers on fruiting varieties such a pyracanthas or cotoneasters should be left, because the fruit or berries will be forming.
Most of your repotting should have been completed but there is still time to work on junipers, olives, serissa, cotoneasters, pyracanthas and, of course, figs. Repot figs once the weather is warm enough and style them at the same time by removing any unwanted branches and long growth.
Defoliation should be done in a couple of months’ time, but do not touch any trees that are unhealthy, as these will not give the desired result. They do not have the strength to produce the new leaves and may be severely set back or could possibly die.
Olives and junipers thrive in alkaline soil; add a small amount of garden lime to the soil by sprinkling it on top of your mix and then water it in. This can be repeated two or three times a year as long as you do not overdo the amount of lime.
As all the pests are out in force now use a systemic insecticide to prevent infestation of lace bug (on azaleas), mealy bug, red spider, scale and aphids. Caterpillars like nothing better than tucking into juicy new foliage! The recent showers of rain have meant that I already have fungal problems on one of my Crepe myrtles, so I have cut back the new growth today and sprayed with eco fungicide.
If doing any wiring at this time, don’t wire too tightly, as trees grow and thicken at an extremely rapid rate during spring and it is easy to forget to check wire. This can result in scarring of the tree, which can take a long time to heal.